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  <div class="section" id="cmp0020">
<span id="policy:CMP0020"></span><h1>CMP0020<a class="headerlink" href="#cmp0020" title="Permalink to this headline">¶</a></h1>
<p>Automatically link Qt executables to <code class="docutils literal notranslate"><span class="pre">qtmain</span></code> target on Windows.</p>
<p>CMake 2.8.10 and lower required users of Qt to always specify a link
dependency to the <code class="docutils literal notranslate"><span class="pre">qtmain.lib</span></code> static library manually on Windows.
CMake 2.8.11 gained the ability to evaluate generator expressions
while determining the link dependencies from <code class="docutils literal notranslate"><span class="pre">IMPORTED</span></code> targets.  This
allows CMake itself to automatically link executables which link to Qt
to the <code class="docutils literal notranslate"><span class="pre">qtmain.lib</span></code> library when using <code class="docutils literal notranslate"><span class="pre">IMPORTED</span></code> Qt targets.  For
applications already linking to <code class="docutils literal notranslate"><span class="pre">qtmain.lib</span></code>, this should have little
impact.  For applications which supply their own alternative WinMain
implementation and for applications which use the QAxServer library,
this automatic linking will need to be disabled as per the
documentation.</p>
<p>The <code class="docutils literal notranslate"><span class="pre">OLD</span></code> behavior for this policy is not to link executables to
<code class="docutils literal notranslate"><span class="pre">qtmain.lib</span></code> automatically when they link to the QtCore <code class="docutils literal notranslate"><span class="pre">IMPORTED</span></code> target.
The <code class="docutils literal notranslate"><span class="pre">NEW</span></code> behavior for this policy is to link executables to <code class="docutils literal notranslate"><span class="pre">qtmain.lib</span></code>
automatically when they link to QtCore <code class="docutils literal notranslate"><span class="pre">IMPORTED</span></code> target.</p>
<p>This policy was introduced in CMake version 2.8.11.  CMake version
3.16.5 warns when the policy is not set and uses <code class="docutils literal notranslate"><span class="pre">OLD</span></code> behavior.  Use
the <span class="target" id="index-0-command:cmake_policy"></span><a class="reference internal" href="../command/cmake_policy.html#command:cmake_policy" title="cmake_policy"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">cmake_policy()</span></code></a> command to set it to <code class="docutils literal notranslate"><span class="pre">OLD</span></code> or <code class="docutils literal notranslate"><span class="pre">NEW</span></code> explicitly.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The <code class="docutils literal notranslate"><span class="pre">OLD</span></code> behavior of a policy is
<span class="target" id="index-0-manual:cmake-policies(7)"></span><a class="reference internal" href="../manual/cmake-policies.7.html#manual:cmake-policies(7)" title="cmake-policies(7)"><code class="xref cmake cmake-manual docutils literal notranslate"><span class="pre">deprecated</span> <span class="pre">by</span> <span class="pre">definition</span></code></a>
and may be removed in a future version of CMake.</p>
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